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Date and Time of the Query: 2019-06-25 T05:54:47 PDT
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Notes for object SDSS-C4 3072

3 note(s) found in NED.


1. 2008ApJ...687..899R
Re:RX J1720.2+2637
RX J1720.2+2637.-The CDG has a blue central region some 13" in radius.

2. 2005ApJ...624..606J
Re:RX J1720.1+2638
RX J1720.1+2638 (z = 0.16): A fairly round, relaxed cluster. It becomes
somewhat elliptical outside the 0.5 Mpc aperture. There were three observations
of this cluster, one very short and the other two at different focal plane
temperatures. We use only the longest observation performed at a focal plane
temperature of -110^deg^C. The 0.5 Mpc aperture fell on three of the ACIS-I
CCDs.

3. 2002ApJS..139..313D
Re:RX J1720.0+2638
5.33. RXJ1720.1+2638 The cluster core is dominated by a single
galaxy with an extended envelope, and the cluster has an optical
appearance similar to A586 and A2261. The peaks in the mass,
light, and number density distributions all coincide well with
the position of the central galaxy. Mazzotta et al. (2001b)
analyze Chandra data of this cluster and find an X-ray surface
brightness peak situated at the position of the central cluster
galaxy. The X-ray surface brightness contours at large radii
have a regular appearance typical for a relaxed system, but
there is a sharp edge ~125 h^-1^ kpc southeast of the cluster
center and a plateau at the opposite, northwest side of the
center. These features mark the extent of a central, dense cold
(kT ~ 4 keV) gas cloud surrounded by a much hotter region with
kT ~ 10 keV. Mazzotta et al. (2001b) interpret this peculiar system
as either the result of a merger in a very late stage or the
result of having a group-sized density perturbation collapse
almost at the same location as a more massive cluster in a way
that has preserved the cooler gas halo of the group-sized
perturbation. A mass estimate assuming hydrostatic equilibrium
and using the gas density properties of a sector located
northwest of the cluster center is consistent with our weak
lensing mass measurements for RX J1720.1+2638 shown in Figure
51, but a similar estimate using the gas density properties in
the southeast sector tends to strongly underestimate the cluster
mass at small radii (Mazzotta et al. 2001b). The sharp jumps in
density and X-ray temperature found by Mazzotta et al. (2001b)
suggest a system in which the central cool gas cloud is moving
with respect to the ambient medium. Such motions would
invalidate the assumption of hydrostatic equilibrium, and
Mazzotta et al. (2001b) suggest that this may be responsible for
the discrepancy between X-ray mass estimates (based on
hydrostatic equilibrium) and strong lensing mass estimates
reported for some clusters. We find three strongly lensed images
inside the envelope of the central galaxy, including a thin,
highly elongated feature 11" southwest of the cluster center. If
we assume a redshift z_s_= 1 for this galaxy and assume that it is
located at the Einstein radius of a spherically symmetric
gravitational lens, the projected mass within ~20 h^-1^ kpc is
7.5 x 10^12^ h^-1^ M_{sun}, consistent with the mass estimate of
Mazzotta et al. (2001b) using Chandra data in the northwest sector
but much higher than their mass estimate using the southeast sector.


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